Corrección de la altura patelar en inestabilidad rotuliana / Correction of patellar height in patellofemoral instability

El manejo de la inestabilidad patelofemoral se basa en una adecuada evaluación de alteraciones anatómicas predisponentes. Patela alta es una de las causas más importantes de inestabilidad objetiva. La alteración biomecánica que ésta produce puede conducir a luxación patelar recurrente, dolor y cambios degenerativos focales. El examen físico es fundamental en la toma de decisiones. La evaluación imagenológica ha evolucionado desde métodos basados en radiografía hacia mediciones en resonancia magnética, que permiten una orientación más acabada de la relación existente entre la rótula y la tróclea femoral. El tratamiento se fundamenta en la corrección selectiva de los factores causales, donde la osteotomía de descenso de la tuberosidad anterior de la tibia y la reconstrucción del ligamento patelofemoral medial son herramientas que deben considerarse racionalmente. Este artículo realiza una revisión de la literatura, otorgando los fundamentos quirúrgicos que explican la importancia del tratamiento específico de patela alta en inestabilidad rotuliana.

Patellofemoral instability management is based on a thorough evaluation of predisposing anatomical factors. Patella alta is one of the utmost causes of objective instability. As a result, biomechanical disturbance can lead to recurrent patellar instability, pain, and focal degenerative changes. Physical examination is paramount in decision making. Imaging evaluation has evolved from X-rays based methods to magnetic resonance measurements, which allows a more accurate assessment of the patellotrochlear relationship. Treatment is based on a selective risk factors correction, where tibial tubercle distalization osteotomy and medial patellofemoral ligament reconstruction must be considered altogether. This article reviews the surgical rationale of patella alta treatment in patellofemoral instability.

PS-TKA with more than 10degrees of Preoperative Posterior Tibial Slope

PURPOSE: We wanted to evaluate the effects of a preoperative posterior tibial slope of more than 10degrees on the extension gap and patellar height during posterior substituted total knee arthroplasty. MATERIALS AND METHODS: One hundred ten posterior substituted total knee arthroplasties were divided into group I (more than 10degrees of preoperative posterior tibial slope, n=56) and group II (less than 10degrees of slope, n=54). Each group was evaluated to compare the frequency of additional distal femoral resections due to an insufficient extension gap and the correlation with the decrease of the patellar bone height. RESULTS: In each group, the preoperative tibial slope was 12.77degrees (+/-3.22degrees) vs. 6.72degrees (+/-2.58degrees), respectively (p=0.000) and the decrease of the posterior slope was 10.74degrees (+/-3.54degrees) vs. 4.78degrees (+/-2.66degrees), respectively, (p=0.000). The frequencies of additional distal femoral resection were 54.5% vs. 46.1%, respectively, (p=0.448) with flexion contracture and 11.8% vs. 34.1%, respectively, (p=0.022) without flexion contracture. The decrease of the patellar bone height was 0.35 (+/-4.79) mm vs. 1.99 (+/-4.78) mm, respectively, (p=0.075). There was weak correlation between the decrease of the patellar bone height and the decrease of the posterior tibial slope (r=-0.253, p=0.016). CONCLUSION: In the group having more than 10degrees of preoperative posterior tibial slope without flexion contracture, the decrease of the posterior tibial slope had to be considered as one of the factors that affected making the extension gap significantly greater during the gap technique and to preserve the patellar bone height.

Change of the Patellar Height and Tibial Inclination after Opening- and Closing-Wedge High Tibial Osteotomy

PURPOSE: We wanted to evaluate the patella height, the tibial inclination and the joint height changes after closing-wedge high tibial osteotomy (CW HTO) and opening-wedge high tibial osteotomy (OW HTO). MATERIALS AND METHODS: The lateral radiographs taken with 30degrees flexion of the knees for 46 CW HTOs and 32 OW HTOs were assessed regarding the patellar height by the Insall-Salvati index (ISI) and the Blackburne-Peel index (BPI) and for the tibial inclination by the Moore-Harvey (MH) method. The average follow up period was 3.6 years (range: 2.0 to 4.7 years). Spearman correlation analysis was used to determine the influence of the two types of HTO with the amount of correction in the frontal plane Hip-Knee-Ankle (H-K-A) axis. The joint height was measured between the fibular head and the lateral tibial plateau. Measurements were made at the preoperative, postoperative and final follow-up periods. RESULTS: In the CW group, both the ISI and BPI were increased at the postoperative and final follow-up periods, while the BPI showed a statistically significant increase (p=0.046). In the OW group, both the ISI and BPI were decreased, while the BPI showed a statistically significant decrease (p=0.007). There was a tendency of a decrease of the tibial inclination in the CW HTO group without statistical significance. But in the OW HTO group, there was a statistically significant increase of the tibial inclination (p=0.012). The frontal plane H-K-A axis correction did not influence the change of the patellar height and tibial inclination in both groups (r<0.3). The joint height measured between the fibular tip and the lateral tibial plateau showed a significant decrease in the CW group (p=0.000), while there was no significant change in the OW group. CONCLUSION: The anatomical alteration of the patellar height was significantly influenced in opposite ways by the two methods of HTO. The BPI was more statistically significant then the ISI for the measurement of the patellar height after HTO. The joint height was significantly decreased in the CW HTO group. These changes should be kept in mind when converting HTO to total knee arthroplasty.

Effect of the Decrease in Tibial Posterior Slope on the Patellar Height after Total Knee Arthroplasty

PURPOSE: To evaluate the effect of the decrease in posterior slope of the tibia on the patellar height after TKA. MATERIALS AND METHODS: One hundred and fifty three cases of TKA (CR type: 43, PS type: 110) were evaluated to measure the posterior slope of the tibia and the patellarheight on lateral radiographs of the knee before and after surgery. Then, we analyzed a correlation between two measurements. RESULTS: The decrease in tibial posterior slope and patellar height was average 6.6 degrees and 1.4mm, there was a weak correlation (r= -0.293, p=0.000), as more decrease in tibial slope, less decrease in patellar height. Comparing CR group with PS group, the decrease of posterior slope of tibia and patella height was average 3.5 vs 7.8 degrees (p=0.000) and 2.2 and 1.2 mm (p=0.146) respectively. There were also correlations (r=-0.438, p=0.003 vs r=-0.228, p=0.017) between two decreases. CONCLUSION: It is considered that the decrease in tibial posterior slope is one of elements influencing in patellar height, and through preoperative radiological examination, estimation of expected decrease in tibial posterior slope is helpful in preserving patellar height in TKA.